From: Waiman Long <waiman.long@hpe.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
Thomas Gleixner <tglx@linutronix.de>,
John Stultz <john.stultz@linaro.org>,
Ingo Molnar <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Borislav Petkov <bp@suse.de>,
Jiang Liu <jiang.liu@linux.intel.com>,
Randy Wright <rwright@hpe.com>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>,
Prarit Bhargava <prarit@redhat.com>, X86 ML <x86@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [RESEND PATCH v4] x86/hpet: Reduce HPET counter read contention
Date: Fri, 12 Aug 2016 17:32:51 -0400 [thread overview]
Message-ID: <57AE4083.90601@hpe.com> (raw)
In-Reply-To: <57AE3D8F.9080202@intel.com>
On 08/12/2016 05:20 PM, Dave Hansen wrote:
> On 08/12/2016 02:10 PM, Waiman Long wrote:
>>> I don't think this is right. If the HPET ever returns the same value
>>> twice in a row (unlikely because it's generally too slow to read, but
>>> it's plausible that someone will make a fast HPET some day), then this
>>> could deadlock.
>> What is the deadlock scenario you are talking about?
> A reader loops waiting for the HPET update by looking for the value to
> change. If the HPET updater does an update, but the HPET itself hasn't
> advanced, it will write the same value as was there before. The reader
> will keep looping thinking there was no update.
I should have addressed this problem in my new v5 patch.
Cheers,
Longman
next prev parent reply other threads:[~2016-08-12 21:33 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-10 18:29 [RESEND PATCH v4] x86/hpet: Reduce HPET counter read contention Waiman Long
2016-08-10 18:37 ` Long, Wai Man
2016-08-10 19:01 ` Prarit Bhargava
2016-08-11 19:32 ` Dave Hansen
2016-08-11 23:22 ` Waiman Long
2016-08-12 0:31 ` Dave Hansen
2016-08-12 17:01 ` Waiman Long
2016-08-12 17:16 ` Dave Hansen
2016-08-12 18:31 ` Waiman Long
2016-08-12 20:18 ` Andy Lutomirski
2016-08-12 21:10 ` Waiman Long
2016-08-12 21:20 ` Dave Hansen
2016-08-12 21:32 ` Waiman Long [this message]
2016-08-12 21:16 ` Dave Hansen
2016-08-12 21:32 ` Waiman Long
-- strict thread matches above, loose matches on Subject: below --
2016-06-17 20:20 Waiman Long
2016-07-13 15:02 ` Waiman Long
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